<template>
  <div class="spec-preview">
    <img :src="imgUrl.imgUrl"/>
    <div class="event" @mousemove="move"></div>
    <div class="big">
      <img :src="imgUrl.imgUrl" ref="bigImg"/>
    </div>
    <div class="mask" ref="mask"></div>
  </div>
</template>

<script>
export default {
  name: "Zoom",
  data() {
    return {
      activeFlag: 0,
    }
  },
  props: {
    imageList: {
      type: Array,
      default: () => {
        return []
      }
    }
  },
  computed: {
    imgUrl() {
      return this.imageList[this.activeFlag] || {}//避免出现假错误：在初始的时候请求没有回来的时候，数据全为空
    }
  },
  mounted() {
    this.$bus.$on("changeImg", (index) => {
      this.activeFlag = index;
    })
  },
  methods: {
    move(event) {
      const {mask, bigImg} = this.$refs;

      let mouseX = event.offsetX;
      let mouseY = event.offsetY;
      let maskX = mouseX - mask.offsetHeight / 2;
      let maskY = mouseY - mask.offsetWidth / 2;
      //设置边界
      if (maskX < 0) {
        maskX = 0
      }
      if (maskX > mask.offsetWidth) {
        maskX =  mask.offsetWidth
      }
      if (maskY < 0) {
        maskY = 0
      }
      if (maskY > mask.offsetHeight) {
        maskY =  mask.offsetHeight
      }

      mask.style.left = maskX + 'px';
      mask.style.top = maskY + 'px';

      //大图移动
      bigImg.style.left=-2*maskX+'px';
      bigImg.style.top=-2*maskY+'px';

    }
  },
}
</script>

<style lang="less">
.spec-preview {
  position: relative;
  width: 400px;
  height: 400px;
  border: 1px solid #ccc;

  img {
    width: 100%;
    height: 100%;
  }

  .event {
    width: 100%;
    height: 100%;
    position: absolute;
    top: 0;
    left: 0;
    z-index: 998;
  }

  .mask {
    width: 50%;
    height: 50%;
    background-color: rgba(0, 255, 0, 0.3);
    position: absolute;
    left: 0;
    top: 0;
    display: none;
  }

  .big {
    width: 100%;
    height: 100%;
    position: absolute;
    top: -1px;
    left: 100%;
    border: 1px solid #aaa;
    overflow: hidden;
    z-index: 998;
    display: none;
    background: white;

    img {
      width: 200%;
      max-width: 200%;
      height: 200%;
      position: absolute;
      left: 0;
      top: 0;
    }
  }

  .event:hover ~ .mask,
  .event:hover ~ .big {
    display: block;
  }
}
</style>
